JP5756764B2 - Uninterruptible transmission equipment - Google Patents

Description

  The present invention relates to an uninterruptible transmission device used in an ATM (Asynchronous Transfer Mode) network or the like.

  Conventionally, as a transmission device such as ATM, there is an uninterruptible transmission device in which a transmission device and a reception device are redundantly connected by a plurality of paths, and transmission can be continued without interruption even when a failure occurs in a certain path. It is known (see, for example, Patent Document 1).

  FIG. 1 is a diagram for explaining a configuration example of a conventional uninterruptible transmission apparatus. In the uninterruptible transmission device 100 shown in FIG. 1, the transmission device 102 duplicates a frame to be transmitted, and outputs the duplicated frame to two different routes (first route 105 and second route 106). Here, the second route 106 is longer than the first route 105, and as shown in FIG. 1, the first route 105 includes one relay device 104a in the middle, and the second route 106 has two in the middle. It is assumed that the relay devices 104b and 4c are included. As described above, when the distance between the routes is different and the number of relay devices is different, a delay difference is generated between the first route 105 and the second route 106. In the case of the example in FIG. 1, the frame that has passed through the first path 105 arrives at the receiving apparatus 103 first, and then the frame that has passed through the second path 106 arrives at the receiving apparatus 103. The receiving apparatus 103 performs delay adjustment of the two frames by delaying the frame from the first path 105, and then selects one frame from these two frames and outputs the selected frame to a subsequent apparatus. According to such an uninterruptible transmission device 100, frame transmission can be continued without interruption even when a failure occurs in one of the paths.

Japanese Patent Laid-Open No. 11-313087

  However, in actual operation, when a communication service is started, it is rare that a plurality of redundant paths are started, and the accuracy of the clock that controls the start of the service, the difference in the protocol processing time associated with the start of the service, the relay Depending on the number of devices, processing delay, etc., a communication service may be started sequentially for each path.

  FIG. 2 is a diagram for explaining a problem when the communication service of the first path 105 is started first and the communication service of the second path 106 is started after that. Regarding the first path 105, all the frames 1 to 5 output from the transmission apparatus 102 have arrived at the reception apparatus 103. On the other hand, regarding the second path 106, frames 1 and 2 have disappeared due to the influence of the delay in starting the communication service, and frames 3 to 5 have arrived at the receiving device 103. In such a case, if the receiving apparatus 103 performs the delay adjustment for the frames after the frame 3, a fluctuation corresponding to the delay difference occurs between the frame 2 and the frame 3 output from the receiving apparatus 103, and seamlessly occurs. May not be able to output frames.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an uninterruptible transmission device capable of preventing the occurrence of fluctuations in an output frame.

  In order to solve the above problems, an uninterruptible transmission device according to an aspect of the present invention includes a transmission device that transmits the same frame to a plurality of routes, and a reception device that receives a frame that arrives from the route. The transmission apparatus receives a dummy frame generation unit that generates a dummy frame for measuring a delay difference between paths, a dummy frame and a normal frame, selects a dummy frame before the communication service starts, and after the communication service starts Includes a selector unit for selecting a normal frame and a frame duplicating unit for duplicating the frame selected by the selector unit and sending it to the path. The receiving device includes a delay difference measuring unit that measures a delay difference between paths based on a difference in arrival times of dummy frames that arrive from the path, and a path after the communication service starts based on a delay difference measurement result using the dummy frames. A delay difference adjustment unit that adjusts the delay so that the normal frames received from the same time are output at the same timing, and a frame selection unit that selects one normal frame from the delay-adjusted normal frames and outputs the selected normal frame to the subsequent stage.

  The dummy frame generation unit may limit the bandwidth of the dummy frame to a predetermined threshold value or less.

  The transmission apparatus may further include a sequence number assigning unit that assigns a continuous sequence number to the frame selected by the selector unit regardless of whether the frame is a dummy frame or a normal frame.

  The delay difference measuring unit may discard the dummy frame after measuring the arrival time of the dummy frame.

  The delay difference adjustment unit may adjust the delay of the normal frame by delaying the first normal frame by the measured delay difference.

  It should be noted that any combination of the above-described constituent elements and a representation of the present invention converted between an apparatus, a method, a system, a program, a recording medium storing the program, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to provide an uninterruptible transmission device that can prevent occurrence of fluctuations in an output frame.

It is a figure for demonstrating the structural example of the conventional uninterruptible transmission apparatus. It is a figure for demonstrating a problem when the communication service of a 1st path | route is started first, and the start of the communication service of a 2nd path | route is started after that. It is a figure which shows the uninterruptible transmission apparatus which concerns on embodiment of this invention. It is a figure for demonstrating operation | movement of the transmitter before communication service start. It is a figure for demonstrating operation | movement of the receiver before the communication service start. It is a figure for demonstrating operation | movement of the transmitter after communication service start. It is a figure for demonstrating operation | movement of the receiver after communication service start.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 3 shows the uninterruptible transmission device 10 according to the embodiment of the present invention. The uninterruptible transmission device 10 shown in FIG. 3 is a transmission device that transmits a frame in an ATM network, and is a redundant device that connects a transmission device 12, a reception device 14, and the transmission device 12 and the reception device 14. The first path 15 and the second path 16 are provided. The first route 15 and the second route 16 are desirably set to different routes in order to avoid that both routes are disconnected simultaneously. Further, the first route 15 and the second route 16 may include one or more relay devices.

  The transmission device 12 has a function of transmitting the same frame to the first path 15 and the second path 16. As illustrated in FIG. 3, the transmission device 12 includes a dummy frame generation unit 17, a selector unit 18, a sequence number assignment unit 19, and a frame duplication unit 20.

  The dummy frame generation unit 17 generates a dummy frame and sends it to the selector unit 18. This dummy frame is a frame for measuring a delay difference between the first path 15 and the second path 16. The bandwidth of the dummy frame is limited to a predetermined threshold value or less. Since the dummy frame is originally traffic in a time zone outside the communication service, the dummy frame is limited to a minimum bandwidth necessary for delay measurement that does not impose other services. In this specification, a frame transmitted in a normal communication service is referred to as a “normal frame”. Further, when simply called “frame”, it means both a dummy frame and a normal frame.

  The selector unit 18 receives the normal frame and the dummy frame from the dummy frame generation unit 17. The normal frame is input from, for example, a device (not shown) arranged at the front stage of the transmission device 12. The selector unit 18 selects one of the normal frame and the dummy frame and outputs it to the sequence number assigning unit 19.

  In the present embodiment, the selector unit 18 selects a dummy frame before starting the communication service and outputs it to the sequence number assigning unit 19. When a normal frame is input before the communication service starts, the normal frame is arranged. On the other hand, the selector unit 18 selects a normal frame after the start of the communication service and outputs it to the sequence number assigning unit 19. If a dummy frame is input after the communication service is started, the dummy frame is discarded.

  The sequence number assigning unit 19 assigns a sequence number to the frame selected by the selector unit 18. When the sequence numbers of the dummy frame and the normal frame are not consecutive, it is determined that the sequence number jumps in the receiving device 14, and it may be determined that a failure such as disconnection has occurred in the communication path. In order to prevent such erroneous determination, the sequence number assigning unit 19 assigns consecutive sequence numbers regardless of whether the input frame is a dummy frame or a normal frame.

  The frame duplicating unit 20 duplicates the frame input from the sequence number assigning unit 19. Then, the duplicated identical frames are sent in parallel to the first path 15 and the second path 16.

  The receiving device 14 has a function of receiving frames arriving from the first route 15 and the second route 16. As illustrated in FIG. 3, the reception device 14 includes a delay difference measurement unit 21, a storage unit 22, a delay difference adjustment unit 23, and a frame selection unit 24.

  The delay difference measurement unit 21 receives frames arriving from the first route 15 and the second route 16. The delay difference measuring unit 21 detects the arrival time of frames and calculates the arrival time difference between frames having the same sequence number. The arrival time difference measured by the delay difference measurement unit 21 is stored in the storage unit 22 as a delay difference measurement result between the first path 15 and the second path 16. The delay difference measurement result includes an arrival time difference between frames having the same sequence number, and information on a route on which the frame arrives first (either the first route 15 or the second route 16). The delay difference measurement unit 21 may calculate an average arrival time difference for a plurality of frames and use the average value as a delay difference between the first path 15 and the second path 16.

  Handling of frames after delay difference measurement differs depending on whether the frame is a dummy frame or a normal frame. When the input frame is a dummy frame, the delay difference measurement unit 21 discards the dummy frame after the delay difference measurement. That is, no dummy frame is output to the delay difference adjusting unit 23 at the subsequent stage. On the other hand, when the input frame is a normal frame, the delay difference measurement unit 21 passes the normal frame toward the delay difference adjustment unit 23.

  The delay difference adjustment unit 23 adjusts the delay based on the result of the delay difference measurement so that normal frames having the same sequence number received from the first path 15 and the second path 16 after the start of the communication service are output at the same timing. I do. The delay difference adjustment unit 23 includes a first delay difference absorption buffer 25 that delays a normal frame from the first path 15 and a second delay difference absorption buffer 26 that delays a normal frame from the second path 16. The delay difference adjustment unit 23 delays the normal frame that arrives by the delay difference stored in the storage unit 22. Thereby, the phases of the first path 15 and the second path 16 are matched, and two normal frames having the same sequence number are output from the delay difference adjusting unit 23 at the same timing.

  The normal frame whose delay is adjusted by the delay difference adjusting unit 23 is input to the frame selecting unit 24. The frame selection unit 24 selects one normal frame from the input normal frames and outputs it to the subsequent stage.

  Next, the operation of the uninterruptible transmission device 10 according to this embodiment will be described. FIG. 4 is a diagram for explaining the operation of the transmission device 12 before the start of the communication service. In the following description, it is assumed that the transmission delay time of the first path 15 is smaller than the transmission delay time of the second path 16.

  FIG. 4 shows a state in which the dummy frame generated by the dummy frame generation unit 17 and the normal frame from the preceding apparatus are input to the selector unit 18. In FIG. 4, two dummy frames are illustrated as an example, but one or more dummy frames may be generated. Before starting the communication service, the selector unit 18 selects a dummy frame and outputs it to the sequence number assigning unit 19. On the other hand, the selector unit 18 discards the input normal frame. The sequence number assigning unit 19 assigns sequence numbers to the dummy frames (in FIG. 4, sequence numbers 1 and 2 are assigned to two dummy frames). The frame duplication unit 20 duplicates the input dummy frame and outputs it in parallel to the first path 15 and the second path 16.

  FIG. 5 is a diagram for explaining the operation of the reception device 14 before the start of the communication service. FIG. 5 shows a state in which the dummy frames with sequence numbers 1 and 2 that have passed through the first path 15 and the second path 16 arrive at the delay difference measurement unit 21.

  The delay difference measuring unit 21 detects the arrival times of the dummy frames that arrive from the first route 15 and the second route 16, and calculates the arrival time difference between the dummy frames having the same sequence number. After the arrival time is measured, the delay difference measurement unit 21 discards the dummy frame.

  The delay difference measuring unit 21 determines the measured arrival time difference as a delay difference between the first route 15 and the second route 16 and stores the difference in the storage unit 22. In addition, the storage unit 22 stores information on the route on which the dummy frame arrives first (in this example, the first route 15). In the example shown in FIG. 5, the arrival time difference is measured for each of the dummy frames of sequence numbers 1 and 2. Therefore, the delay difference measuring unit 21 may use the arrival time difference for one of the dummy frames of sequence numbers 1 and 2 as the delay difference between the paths. Alternatively, the delay difference measurement unit 21 may calculate the average arrival time difference for the dummy frames of sequence numbers 1 and 2 and use this average value as the delay difference between the paths. When the average value is used, the delay difference can be measured more accurately.

  FIG. 6 is a diagram for explaining the operation of the transmission device 12 after the start of the communication service. After starting the communication service, the selector unit 18 selects a normal frame and outputs it to the sequence number assigning unit 19. On the other hand, the selector unit 18 discards the input dummy frame. The sequence number assigning unit 19 assigns a sequence number to the normal frame. As described above, the sequence number assigning unit 19 assigns consecutive sequence numbers regardless of whether the input frame is a dummy frame or a normal frame. In this example, since sequence numbers 1 and 2 are assigned to the dummy frame, the sequence number assigned to the normal frame starts from 3. The frame duplicating unit 20 duplicates the input normal frame and outputs it in parallel to the first path 15 and the second path 16.

  FIG. 7 is a diagram for explaining the operation of the receiving device 14 after the start of the communication service. FIG. 7 illustrates a state in which normal frames having sequence numbers 3 to 6 that have passed through the first path 15 and the second path 16 arrive at the delay difference measurement unit 21.

  The delay difference measuring unit 21 detects the arrival time for the normal frame and calculates the arrival time difference between the normal frames having the same sequence number. In this example, when the normal frame with the sequence number 3 from the first path 15 is received, the normal frame with the sequence number 3 from the second path 16 is not received. The arrival time difference is measured with the reception of the normal frame with the sequence number 3 from the path 16. When the arrival time difference is measured for the normal frame of sequence number 3, the delay difference measurement unit 21 updates the delay difference measurement result stored in the storage unit 22. The same applies to normal frames after sequence number 4.

  When the input frame is a normal frame, the delay difference measurement unit 21 passes the normal frame toward the delay difference adjustment unit 23. FIG. 7 illustrates a state in which normal frames having sequence numbers 3 and subsequent from the first path 15 are input to the delay difference adjusting unit 23 first. The delay difference adjustment unit 23 refers to the delay difference measurement result stored in the storage unit 22 and delays the normal frame from the first path 15 by the delay difference measured using the dummy frame. As a result, as shown in FIG. 7, two normal frames having the same sequence number are output from the delay difference adjustment unit 23 at the same timing. As described above, the delay difference measurement result stored in the storage unit 22 is updated when the normal frame with the sequence number 3 arrives from the second path 16 and the arrival time difference is measured with respect to the normal frame with the sequence number 3. Is done. Therefore, the delay difference measurement result referred to by the delay difference adjustment unit 23 is changed from the middle to the delay difference measurement result measured using the normal frame.

  The normal frame output from the delay difference adjustment unit 23 is input to the frame selection unit 24. The frame selection unit 24 selects one of the normal frame from the first path 15 and the normal frame from the second path 16 and outputs it to the subsequent stage.

  As described above, in the uninterruptible transmission device 10 according to the present embodiment, the delay difference between the paths is measured using the dummy frame before the communication service is started, and the delay difference measurement result after the communication service is started. Based on this, delay adjustment of the normal frame is performed. Since the delay adjustment of the normal frame is preferably performed from the time when the communication service is started, the occurrence of fluctuation in the output frame as described in FIG. 2 can be prevented.

  In the above-described embodiment, the transmission path of the uninterruptible transmission device 10 is made redundant by two paths, but may be made redundant by three or more paths.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications are possible depending on the combination of each component and each processing process, and such modifications are within the scope of the present invention. is there.

  DESCRIPTION OF SYMBOLS 10 Uninterruptible transmission apparatus, 12 Transmission apparatus, 14 Reception apparatus, 15 1st path | route, 16 2nd path | route, 17 Dummy frame production | generation part, 18 Selector part, 19 Sequence number assignment part, 20 Frame duplication part, 21 Delay difference measurement Unit, 22 storage unit, 23 delay difference adjustment unit, 24 frame selection unit, 25 first delay difference absorption buffer, 26 second delay difference absorption buffer.

Claims (4)

An uninterruptible transmission device comprising: a transmission device that sends the same frame to a plurality of paths; and a reception device that receives a frame arriving from the path,
The transmitter is
A dummy frame generator for generating a dummy frame for measuring a delay difference between the paths;
A selector unit which dummy frame and a normal frame are entered, the prior communication service start without sending a normal frame from the transmitting device selects a dummy frame, the communication service start after sending a normal frame from the transmitting device Is a selector part for selecting a normal frame,
A sequence number giving unit for assigning a continuous sequence number to the frame selected by the selector unit regardless of whether the frame is a dummy frame or a normal frame;
A frame duplicating unit that duplicates a frame to which a sequence number is assigned by the sequence number assigning unit and sends the frame to the path;
The receiving device is:
A delay difference measuring unit that measures a delay difference between the paths based on an arrival time difference of a dummy frame arriving from the path;
Based on the result of delay difference measurement using a dummy frame, a delay difference adjustment unit that performs delay adjustment so that normal frames received from the path after the start of the communication service are output at the same timing;
A frame selection unit that selects one normal frame from the delay-adjusted normal frame and outputs the selected frame to the subsequent stage;
A failure determination unit that detects whether or not the sequence numbers of the received frames are continuous, and determines that a failure has occurred in the path when not continuous ,
A non-instantaneous transmission device characterized by that.   The uninterruptible transmission device according to claim 1, wherein the dummy frame generation unit limits the bandwidth of the dummy frame to a predetermined threshold value or less. The delay difference measuring unit after measuring the arrival time of the dummy frame, uninterrupted transmission apparatus according to claim 1 or 2, characterized in that discarding the dummy frame. The delay difference adjustment unit, uninterrupted transmission apparatus according to claim 1, wherein the adjusting the delay of the normal frame by delaying the measured delay difference by arrival of the ordinary frame 3 .

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